In a conventional automatic storage and retrieval apparatus, two storage areas are formed by vertically and horizontally arranging racks serving as article storage places in the form of a matrix with front surfaces of the article storage places opposed to each other with a predefined space or longitudinal aisle extending therebetween. A vertical column is moved along the front surfaces of the storage areas to introduce or extract articles into or from respective racks of the storage areas by a picker vertically movably provided on the column.
In the aforementioned structure, a vertically extended large column must be driven horizontally in order to move the pickers to a desired rack, whereby considerable power is required causing increasing operating cost. Further, since subsequent introducing or extracting operations cannot be performed until an article is completely introduced into or extracted from a desired rack, introducing or extracting processing takes a great deal of time and is only effected in an inefficient manner. Further, the column and the picker must be connected with a control device for controlling the same by control wires, and hence wiring the installation is difficult.
In the aforementioned conventional automatic storage and retrieval apparatus, a forklift mechanism for picking up a container from the lower side of the container or an extracting arm mechanism formed to be engageable with a fitting portion provided on the front or side surface of the container has been employed as a mechanism of the picker for extracting the container for receiving the article from the storage area onto the picker and returning the same from the picker onto the storage area. However, the forklift mechanism is disadvantageous in space since the containers must be arranged with sufficient intervals in the vertical direction to allow not only lifting of the container from its supports prior to extraction, but also allowing space for a heavy arm section to support the weight, while the extracting arm mechanism is applicable only to specific containers having the fitting portion on the front or side surfaces.
The known automated storage and retrieval systems having in common at least one matrix of storage locations for modular removable containers, tote boxes, or bins, a stacker crane assembly, which moves horizontally along an aisle in front of or between storage locations, a vertically movable platform on the stacker crane assembly, and suitable motors, position sensors, limit switches, and a selected control system to enable positioning the platform at a suitable X-Y coordinate address representing a selected storage location in the storage matrix.
Various types of extraction devices have been proposed in conjunction with the automated storage and retrieval systems. Magnetic extractors have been used to engage a magnetic plate attached to the end of each bin or container. This is adaptable to very light containers, and because of the space occupied by the magnet assembly on the platform, it is suitable only for extraction and subsequent replacement back in the same lateral direction from which the container was extracted. Hook extractors have also been adapted to cooperate with a special handle on the end of the container, by rotating a hook into an upright position inside the inverted L-shaped recess in the handle. The extracted container is removed onto a pair of endless belts which support the container and reduce the strain on the hook. The success of this type of extraction system depends on precise positioning of the handles of the modular containers residing throughout the matrix and misalignment of a particular container may result in faulty engagement of the system. Also a cost penalty is paid as each bin must have a handle welded at each end of the bin.
Another type of extraction system involves insertion of a lifter platform beneath a container, lifting and withdrawing it. This system results in much lost space in the storage matrix, since vertical spacing between container supports must be provided to allow insertion of the lift or shuttle platform and lifting of the container from the supports prior to extraction. The vertical lifting motion also wastes time, making the overall system less efficient. The present invention seeks to reduce and, where possible, eliminate the perceived disadvantages of the conventional automatic storage and retrieval systems including the extractor mechanism.